US2024321A - Method and means for controlling the tone of a radio set - Google Patents

Description

Dec. 17, 1935. L WILLGING' 2,024,321

METHOD AND MEANS FOR CONTROLLING THE TONE OF A RADIO SET Filed March 25, 1931 INVE N TOR.

A TTORNEYS Patented Dec. 17, 1935 UNITED STATES PATENT OFFICE METHOD AND MEANS FOR CONTROLLING THE. TONE OF A RADIO SET Application March 23, 1931, Serial. No. 524,419

4 Claims.

My invention is addressed to means for effecting so-called tone control inradio sets; but it is an object of my invention to provide means and a method for tone control which goes beyond the mere relative suppression of undesired frequencies, and accentuates the desired frequency range.

It isan object of my invention to provide in a tone control means and a method, when, for example, the treble range is desired, not only to suppress the lower frequencies, but to reinforce and build up the volume of the higher frequencies.

Conversely, it is my object when stronger bass values are desired, to provide a means and method not only to suppress the higher frequencies, but also build up, reinforce, and strengthen the lower frequencies.

Consequently, it is my object to achieve in a tone control, adequate and full range variation of tone, so called, without substantial change in 7 volume.

It is a further object of my invention to provide a tone control which is continuously variable from extreme treble to extreme bass.

These and the more specific objects of my in-, vention which will be set forth hereinafter, or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that certain construction and arrangement of parts of which I shall now describe a preferred embodiment, reference being had to the drawing in which I have shown only so much of a radio circuit as is necessary to the comprehension of my invention.

My method is applied to the audio frequency portion of a radio receiving system, but is not restricted to any particular type of set or circuit.

In the practice of my invention I raise the tone, so called, by accentuating the higher frequencies. This is accomplished by regeneration at the higher frequency, involving the feeding from the treble position, resistance is introduced into.- the. feed back circuit in such a Way as ultimately to eliminate the said regeneration. During the shift however, resistance is progressively taken out of a parallel resonance circuit compris- 5 ing the primary of an audio frequency transformer and a condenser of desired capacity so that the low frequencies are augmented simultaneously with the attenuation of the high frequencies. 10

This is accomplished by inexpensive mechanism which comprises only a potentiometer and two fixed capacities; and with this explanation my drawing will be clear. I have shown at I an audio frequency tube, the plate 2 of which feeds 15 the primary 3 of an audio frequency transformer indicated generally at 4. The secondary 5 of this transformer feeds the grid 6 of a succeeding audio frequency tube 1. The plate 8 of this tube is connected through a fixed capacity 9, to one 20 end of the resistance element of a potentiometer Ill. The plate 2 of, the tube l is connected through the fixed capacity H to the arm or variable contact point l2 of the potentiometer Ill. The other end of the resistance element of the 5 potentiometer is'connected by a lead I 3 to the grounded side of the primary of the transformer 4.

When the contact arm I2 is in the extreme left hand position in the figure, the condenser II will 30 in effect be connected in parallel across the primary of the transformer 4 resonating it at some low frequency range, thus accentuating the low notes. As the arm I2 is moved toward the right in the figure, more and more resistance is inserted 35 into this resonant circuit. At the same time however, resistance is removed progressively from a feed back circuit connection between the plate 8 of tube 1 and the primary 3 of transformer 4. This feed back connection comprises 40 1 in series the capacities 9 and H, and it will be noted that the connection is such that energy is fed back in proper phase relationship for regeneration.

The values of capacities 9 and II and of the 45 resistance of the potentiometer it! may be readily selected. for a desired tone control with reference to the other constants of the set. Tone control is, as explained, achieved by the operator merely by movement of the potentiometer arm. The change in response is gradual, and any compromise may be reached between the two extremes. Of course the regenerative circuit may be caused to respond to low frequencies and the resonance circuit to high frequencies, if desired. 5

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a radio set an audio frequency tube and circuit means connecting the plate of said tube with the primary of a preceding audio frequency transformer in proper phase for regeneration, a circuit comprising a condenser paralleled across the primary of an audio frequency transformer preceding said tube, and controllable means for introducing resistance in inverse proportion into the two circuits.

2. In a radio set a tone control comprising an audio frequency tube, a connection comprising a capacity between said tube and the primary of a preceding audio frequency transformer, a connection comprising a capacity paralleled across said primary, and means for varying the response effects of the resonance and regeneration circuits formed by said connections, said means comprising a potentiometer common to both circuits.

3. In a radio set a tone control comprising in combination with an audio tube, and a preceding audio transformer, a potentiometer, a lead comprising a capacity connecting one end of the resistance element of said potentiometer to the plate of said tube, a lead connecting the other end of said resistance-element to the grounded.

side of the primary of said transformer, and a connection including a capacity between the variable arm of said potentiometer and the ungrounded side of said transformer.

4. In a radio set a tone control comprising in combination with an audio frequency tube and a preceding audio frequency transformer, a potentiometer, a connection including a fixed capacity between said potentiometer and the plate of said tube, a connection including a fixed capacity between said potentiometer and the primary of said transformer, said connections effecting a feedback circuit for energy in proper phase for regeneration, said circuit including both said capacities, and a connection between said potentiometer 20 LOUIS F. WILLGING.

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